Enter the text here that is the new abstract information for your application. This section must be no longer than 30 lines of text. Substance use disorder (SUD) is a chronic, relapsing disease. However, current systems of care typically respond to SUD as an acute problem requiring short-term residential and/or outpatient treatment. As currently treated, people with SUD continue to have high relapse rates, with few opportunities for long-term recovery and relapse prevention supports. One approach to continuous care is for substance use counselors to engage clients in systematically monitoring their own progress and to offer therapeutic feedback in response. This approach aligns with the Institute of Medicine's explicit recommendation for the use of client monitoring systems, which offer continuous monitoring and feedback, allowing the counselor to intervene when needed. The SUD field has begun to explore promising strategies for using monitoring and feedback, including through the use of technologies such as telephone and mobile devices. Building on NIDA-funded research on RecoveryTrack, a computer-based client outcomes monitoring system (OMS), the Center for Social Innovation, LLC (C4) has partnered with Treatment Research Institute (TRI) to develop and evaluate RecoveryTrack- Mobile: A Monitoring and Feedback Intervention (RT-M). The goal of this intervention, to be developed into a mobile application, is to mitigate the risk of relapse among clients during and after outpatient treatment, using an evidence-based OMS assessment. This extends continuous monitoring beyond the clinical setting and into a client's day-to-day environment. Clients will complete core RecoveryTrack assessment questions weekly and daily, and the results will be used to prompt feedback or support from the counselor and family, friends, and/or sponsors that the client has elected to connect with the app. The app will include recovery supports such as motivational and alert messages, information, and resource links that promote recovery and wellness. During Phase 1, we will conduct a small-scale pilot study that is designed to evaluate feasibility and counselor and client acceptability of RT-M, and to determine whether RT-M supports clients' post-discharge functioning. We will use quantitative and qualitative methods to evaluate the product/intervention prototype in order to provide proof of concept for a larger Phase 2 effectiveness study. We will recruit a sample of clients (n=30) and counselors (n=6) from a large medical center in Philadelphia, PA that offers outpatient drug and alcohol services. Quantitative data will be collected through baseline and follow-up assessments (one-month post discharge), using instruments with strong psychometric properties to measure changes in substance use and other relevant functional indicators, as well as urine testing. Qualitative and quantitative data will be collected on counselors and clients, to understand their use of and experiences with the app and the intervention, and suggestions for Phase 2. The project will be informed and enhanced by a Community Advisory Board of former clients and counselors.